The lawmakers argued that the FAA could make cuts in other areas of its budget.

"We ask that you identify lower priority spending elsewhere in the FAA’s budget for reduction," the lawmakers wrote. "It is deeply troubling that the agency seems intent on proceeding with the closure of key air traffic control assets absent adequate safety data and study.”

The FAA has said that the flight tower closures will not affect most major airports where most commercial flights operate from because the facilities that have been identified are mostly at small regional airports.

But the lawmakers said Friday that closing small air towers would still impact the safety of the overall national aviation system.

"As you are well aware, contract towers have long played an integral role in the agency's efforts to manage the safety and efficiency of the nation's complex airspace," they wrote. "The decision to shutter contract towers on such a wide-scale basis is unprecedented."

The FAA had originally announced that it would begin closing the flight towers on April 7, but the agency pushed the closures back to June 15 after facing pressure from both lawmakers and airports.

At least three airports have filed lawsuits against the FAA to block the air tower closures completely.

The lawmakers said Friday that they wanted more information about the factors that contributed to the selection of the flight towers the FAA has marked for closure.

"Despite the serious concerns expressed by elected representatives in the House and Senate on a bipartisan basis, as well as by local officials, business leaders, airports, air traffic controllers, general aviation operators and businesses, state aviation officials and other concerned citizens, the FAA has yet to address the impact this action may have on aviation system safety or efficiency," the legislators wrote.

"It is deeply troubling that the agency seems intent on proceeding with the closure of key air traffic control assets absent adequate safety data and study," the lawmakers continued. "We recognize the FAA faces difficult choices, but in this instance we remain opposed to the FAA's actions and will continue to urge action to keep contract towers open and operational."

The FAA has said it will use the extra time provided by the delay in closing the towers it announced last week to assuage lawmaker's concerns about the airports that were selected.